Communicating distinct data over a single frequency using multiple linear polarized signals

ABSTRACT

A method and system for transmitting three distinct electromagnetic signals on a same frequency are provided. One or more transmitting devices transmit a first data signal and an inverse of the first data signal in two orthogonal linear polarities of an antenna maintaining their inverted phase relationship and a same amplitude as propagated. Transmitting devices also transmit a second data signal in a linear polarity with a 45 degree rotation around the transmit axis of the first data signal. Transmitting devices also transmit a third data signal in linear polarity orthogonal to the second data signal and consequently 315 degree rotation around the transmit axis from the first data signal.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of U.S. patentapplication Ser. No. 13/477,084, titled “Communicating Distinct Dataover A Single Frequency Using Multiple Linear Polarized Signals”, filedMay 22, 2012 in the United States Patent and Trademark Office. Thespecification of the above reference patent application is incorporatedherein by reference in its entirety.

BACKGROUND

The method and system disclosed herein, in general, relates toinformation communication. More specifically, the method and systemdisclosed herein relates to communicating multiple channels of distinctdata, simultaneously, over the same frequency using multiple linearpolarized signals.

Current satellites and ground based radios typically reuse frequenciesby transmitting signals in two orthogonal polarities of one of twopolarization schemes, namely, left and right hand circular polarization,or vertical and horizontal linear polarization. Normally, no more thantwo signals can be transmitted along the same or proximate path, eachoccupying one of two orthogonal polarizations in only one of the twopolarization schemes. U.S. Pat. No. 7,590,191 B1, and U.S. Pat. No.7,957,425 as well as U.S. application Ser. No. 13/237,846 commonlyassigned to the applicant have described methods to increase capacity oftransmitted electromagnetic signals by using a combination of circularlyand linearly polarized signals. There is a need for a method forincreasing data carrying capacity using only linearly polarized signals.

In linear polarization, the electric component or the magnetic componentof an electromagnetic wave is confined to within a single plane alongthe direction of propagation of the electromagnetic wave. Linearlypolarized signals are either horizontally polarized or verticallypolarized, each being orthogonal to the other, that is, rotated 90degrees around the transmit axis. They do not interfere with each otheronce transmitted and using polarized receive antennae are receivedseparately without interference from the other.

Polarization of an electromagnetic signal can be established by variousmethods, for example, through the shape of the radiation elements in theantenna in the case of a lower frequency antenna, or by a dipole feedinginto a horn and reflector of a parabolic antenna in a higher frequencyband, or by specialized emitters or by filters in the case of light.

A basic principle of electromagnetic waves is the principle of linearsuperposition: “when two or more waves are present simultaneously at thesame place the resultant wave is the sum of the individual waves.”Physics 3rd Edition by Cutnell/Johnson, Wiley and Sons, 1995. ISBN0-471-59773-2, page 521. “Inverse signals” are two same signals that areexactly 180 degrees out of phase so that when two inverse signals of thesame amplitude are combined, they sum to zero power, canceling eachother.

As used herein, the term “feed horn” or “feed” refers to an apparatusthat includes both a horn and a transducer, also called a polarizer. Thetransducer may contain a radiator or dipole that emits polarized signalsfor transmission. A typical transducer is a mechanical device that isattached to the horn. The horn illuminates the antenna, as well as picksup already polarized data signals for reception and passes the receivedsignals on to the transducer. A transducer also routes the data signalsfrom a transmission side of input flanges to the horn or from the hornto a reception side of output flanges.

As used herein, “data signal” refers to an electromagnetic signalmodulated to carry information of any kind. “Information signal” and“data signal” both refer to an electromagnetic signal that containsencoded information to be communicated.

A frequency band is a contiguous set of frequencies with a centerfrequency and multiple side frequencies. Two signals of the “samefrequency” means that at least one of the frequencies of the frequencyband used to transmit a data signal is the same for both signals, i.e.,at least part of the band of frequencies overlaps. Both data signals canoccupy the same band or partially overlapping bands. The data signalscan convey digital or analog information. The “transmit axis” is theline between a transmitting antenna and a corresponding receive antenna.

Electromagnetic waves do not interact when transmitted through a nonabsorbing media such as space. Horizontal and vertical linearlypolarized data signals do not modify each other once transmitted andpass through space without interference. Until now, due to the noise andinterference involved, only two data signals in a single polarizationscheme could typically be used to communicate distinct data signals onthe same frequency. This means on a given frequency, a maximum of twodata signals can be transmitted simultaneously, one on each polarity ofthe chosen polarization scheme. There is a need for transmittingadditional data signals using only linear polarization schemes resultingin increased data carrying capacity. There is a need for a method totransmit up to, for example, three data signals on a same frequencysimultaneously by using linear polarized signals.

Hence, there is a long felt but unresolved need for communicatingadditional distinct data over a single frequency using multiple linearlypolarized data signals.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in asimplified form that are further disclosed in the detailed descriptionof the invention. This summary is not intended to limit the scope of theclaimed subject matter.

The method and system disclosed herein addresses the above stated needfor simultaneously communicating three distinct data signals over a samefrequency instead of two, and for doubling capacity in mobile systems.The method and system disclosed herein addresses the above stated needfor communicating additional distinct data over a single frequency usingmultiple linearly polarized electromagnetic emissions resulting in anincrease in capacity. The method and system disclosed herein can be usedin any media where electromagnetic signals can be polarized. A datasource provides multiple data signals conveying first data, second dataand third data, wherein the data signals are of the same frequency. Eachdata signal is a stream of information, analog or digital, encoded byany of the known means onto a transmit carrier of selected transmitfrequency. The data signals comprise a first data signal conveying firstdata, a second data signal conveying second data, and a third datasignal conveying third data. One or more transmitting devices transmitthe first data signal and an inverted copy of the first data signal intwo orthogonal linear polarities of a linear polarization scheme. Atransmitting device also transmits the second data signal in a linearpolarity with a 45 degree rotation around a transmit axis from eitherthe first data signal or from the inverse of the first data signal. Thesecond data signal is transmitted from either a same location as thefirst data signal or a different location from the first data signal.

One or more receiving stations receive the transmitted first datasignal, the inverse of the first data signal, and the second datasignal.

In an embodiment, the transmitting devices transmit a third data signal(S3) in linear polarity, wherein the third data signal is transmittedorthogonal to the second data signal. The third data signal istransmitted with a 315 degree or equivalently a ±45 degree rotationaround the transmit axis from either the first data signal or theinverse first data signal and, consequently, orthogonal to the seconddata signal.

In this embodiment, the first data signal (S1) and an inverted copy ofthe first data signal (S1 ⁻¹), which is 180 degrees out of phase, arepolarized in orthogonal linear polarities, for example, horizontal andvertical polarities, and are transmitted in orthogonal polarizationsfrom the same location. These signals are transmitted from the samelocation to maintain the inverted phase relationship as the signalpropagates through the medium. Before transmission, the phase andamplitude of the first data signal and the inverse of the first datasignal are adjusted as necessary for enabling the first data signal andthe inverse of the first data signal to cancel each other out whenreceived together resulting in combination. Complete cancellation of twoelectromagnetic signals occurs when two identical signals that are 180degrees out of phase and of equal amplitude are combined or receivedtogether. The resulting transmission of S1 and S1 ⁻¹ has nulls at 45degree, 135 degrees, 225 degrees and 315 degrees when looking around thetransmit axis. The nulls of the two transmitted inverse signals occur at±45 degrees from the vertical and identically ±45 degrees from thehorizontal.

The second data signal S2 is transmitted in the null of the first datasignal at 45 degrees. The third data signal S3 is transmitted in thenull of the first data signal at −45 degrees, and orthogonal to thesecond data signal S2. A receive feed aligned to the transmit polarityof the second data signal receives zero interference from the twoinverse first data signals since the second data signal is transmittedin a null of the inverse signals S1 and S1 ⁻¹. The second data signal isorthogonal to the third data signal which results in zero interferencefrom the third data signal. Consequently, a correctly aligned receiveantenna receives the second data signal S2 with zero interference fromthe first data signals S1 and S1 ⁻¹ or the third data signal S3. Thesecond data signal is received at the receiving stations in both theorthogonal linear polarities. The received second data signal in one ofthe orthogonal linear polarities is combined, in phase, with thereceived second data signal in the other of the orthogonal linearpolarities to reduce interference from the first data signal and theinverse of the first data signal.

A receive feed aligned to the transmit polarity of the third data signalreceives zero interference from the two inverse first data signals sincethe third data signal is transmitted in a null of the two inverse firstdata signals. The third data signal is orthogonal to the second datasignal which results in zero interference from the second data signal.Consequently, a correctly aligned receive antenna receives the thirddata signal S3 with zero interference from the first data signals S1 andS1 ⁻¹ or the second data signal S2.

To receive the first data signal, an antenna with both vertical andhorizontal receive polarities is used. The antenna feed polarities needto be aligned with the S1 transmit polarities to pick up the selectedtwo inverse signals, S1 and S1 ⁻¹, in the two receive linear ports,vertical and horizontal. One of the sets of data signals received ineither the horizontal polarity or the vertical polarity is inverted, andthen one of the two sets of received signals is phase adjusted ifnecessary such that the linear S1 signals match in phase. Then thereceived and inverted signal is summed with the signal received in theother polarity. When one signal is inverted and summed with the other,the linearly polarized data S1 signals match each other, therebyincreasing the signal strength of the first data signal. One of the twoS1 signals was inverted prior to transmission and then again uponreception, resulting in no net phase shift. Since both the interferingsecond and third polarized data signals are received at equal levels inboth horizontal and vertical linear ports, and one of the two receivedsignals in one polarity is inverted and then summed with the same signalin the other polarity, the interfering second and third data signalsnegate at summation, resulting in negligible interference to the firstdata signal S1.

The data signals S2 and S3 can be transmitted from the same location asS1 and S1 ⁻¹, or from a different location. The data signals S2 and S3can be transmitted together from the same location or from differentlocations. The rotation around the transmit axis is essential.

In an alternative embodiment, both S2 (vertical) and S3 (horizontal)data signals are the same signal transmitted in phase. The two inverseorthogonal signals carry a first data signal as usual. However, insteadof carrying distinct second and third data signals, both the second andthird signals, horizontal and vertical, carry the same second datasignal. In this embodiment, when both horizontal and verticalpolarizations are received and summed in phase for detecting S2, therotation around the transmit axis of the receive antenna in relationshipto the rotation around the transmit axis of the transmit antenna doesnot matter allowing for use in mobile applications or applications wherethe rotation of the transmit polarity is unknown or varies inrelationship to the receive polarity. Upon summation of the receivedhorizontal and vertical polarities, any interference from the datasignals S1 and S1 ⁻¹ cancel out and only the second data signal S2remains. The antenna design and signal processing disclosed herein makesthe rotation of the transmit antenna for the two inverse first datasignals in relation to the receive antenna uncritical for reception.

Upon summing by combining the two receive polarities, horizontal (H) andvertical (V), of the receive antenna, the interfering inverse S1 signalssum to zero and the desired second data signal S2, transmitted inhorizontal and vertical polarities, sums to one (full power) for allrotations of the receive antenna around the transmit axis. This meansthat if the receive antenna can receive both polarities H and V at equallevels, the rotation around the transmit axis does not matter. If thereis another rotation along the Z axis, for example, away or toward thetransmitter, in some circumstances, it is possible to adjust thereceived levels of each pole prior to summation such that the amplitudesof the interfering received S1 signals match and cancel.

In order to detect the first data signal S1 without interference fromthe second data signal S2, two orthogonal receive poles receivingsignals at equal strength are used, or the strength of the two poles iselectronically adjusted such that the amplitudes of the two polaritiesare equal. In order to detect the S1 data signal, the received signalfrom one linear receive element is inverted and summed with the receivesignal in the orthogonal polarity. This eliminates the interfering S2data signal. However, it can be seen that a rotation of the receiveelements around the transmit axis causes a drop off in signal strengthas the receive antenna dipole approaches 45 degrees from the transmitdipole, and then the signal gain starts to rise again requiring somealignment of the receive poles to the S1 and S1 ⁻¹ transmit poles.

Since the signal strength of the first data signal S1 varies as therotation of the receive antenna changes, various choices are availableto maintain the signal strength of the data signal S1. One choice is toprovide minor alignment of the receive antenna polarities with thetransmit polarities. For example, if the receive antenna can bemaintained within a fifteen degree rotation of the transmit antenna, thereceive antenna would receive power at about 75% of a fully alignedantenna. Alternatively, in another embodiment, the alignment problem isaddressed by having two sets of orthogonal receive antenna each rotatedat a 45 degree rotation around the transmit axis from the other, andeach capable of receiving both horizontal and vertical polarities. Anelectronic controller at the receiving end can select the orthogonaldipole pair with the higher S1 data signal strength, thus allowing acomplete 360 degree rotation of the antennae around the transmit axiswithout a complete loss of signal. A rotation along the transmit axiscan be compensated for by increasing the signal strength of either thehorizontal or vertical received poles to match the other.

Once a dipole pair is selected, the first data signal and the inverse ofthe first data signal are received at the receiving stations in the twopolarities of the selected dipole pair. One of the first data signal andthe inverse of the first data signal is inverted and summed with theother of the first data signal and the inverse of the first data signalto yield the first data signal at an increased strength. The receivedsecond data signal cancels out at summation.

In a three dimensional receive antenna, multiple sets of dipoles can belocated along all three axis. The electronic controller can then selectfrom the best pair of orthogonal dipoles at any particular instant.

Using the above techniques, data carrying capacity can be increased inany transmission medium that allows for transmission of polarizedelectromagnetic signals. The method and system disclosed herein findsapplications, for example, in satellite communications systems,microwave radio systems, and systems using polarized light.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, is better understood when read in conjunction with theappended drawings. For the purpose of illustrating the invention,exemplary constructions of the invention are shown in the drawings.However, the invention is not limited to the specific methods andcomponents disclosed herein.

FIG. 1 illustrates a method of transmitting electromagnetic signals overa single frequency using multiple linearly polarized data signals.

FIG. 2 illustrates a system for transmitting electromagnetic signalsover a single frequency using multiple linearly polarized data signals.

FIG. 3 exemplarily illustrates nulls of the first data signal S1 and theinverse of the first data signal S1 ⁻¹.

FIG. 4 exemplarily illustrates the relative rotation around the transmitaxis of the first data signal S1, the inverse of the first data signalS1 ⁻¹, a second data signal S2, and a third data signal S3.

FIG. 5 exemplarily illustrates a flow chart for reception of datasignals at a receiving station for acquiring the first data signal.

FIG. 6 exemplarily illustrates a flow chart for reception of datasignals at a receiving station for acquiring the second data signal whenS2 and S3 carry the same data signal.

FIG. 7 exemplarily illustrates a configuration for a gyroscopic receiveantenna.

FIGS. 8A-8B exemplarily illustrate a typical implementation of themethod to transmit and receive three distinct data signals on the samefrequency simultaneously.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a method of transmitting electromagnetic signals overa single frequency using multiple linearly polarized data signals. Adata source provides 101 multiple data signals conveying first data,second data and third data, wherein the data signals are of the samefrequency. The data signals comprise a first data signal conveying firstdata, a second data signal conveying second data, and a third datasignal conveying third data. Each data signal is a stream of dataencoded by any of the known means onto a transmit carrier of theselected transmit frequency. One or more transmitting devices transmit102 the first data signal and an inverse of the first data signal in twoorthogonal linear polarities of a linear polarization scheme.

Transmitting devices also transmit 103 the second data signal in a powernull of either the first data signal or the inverse of the first datasignal. The second data signal is transmitted in a linear polarity witha 45 degree rotation around the transmit axis from either the first datasignal or the inverse of the first data signal. The second data signalis transmitted from either a same location as the first data signal or adifferent location from the first data signal.

In an embodiment, the transmitting devices also transmit 104 the thirddata signal in the power null of either the first data signal or theinverse of the first data signal. The third data signal is transmittedin linear polarity with a 315 degree or equivalently a −45 degreerotation around the transmit axis of either the first data signal or theinverse of the first data signal. The second data signal and the thirddata signal are orthogonal to each other at the point of transmission.The third data signal is transmitted from either the same location asthe first data signal and/or the second data signal. Alternatively, thethird data signal is transmitted from a location different from thefirst data signal and/or the second data signal.

One or more receiving stations receive 105 the transmitted first datasignal, the inverse of the first data signal, the second data signal,and the third data signal.

The method disclosed herein increases data carrying capacity in anelectromagnetic transmission system, allowing three distinct datasignals to be transmitted simultaneously over the same frequency. Themethod and system disclosed herein transmits the three data signalsusing linearly polarized electromagnetic emissions.

The first data signal S1 is divided into two identical copies. One ofthese copies is inverted, that is, phase changed by 180 degrees. Thesetwo inverse first data signals are transmitted in two orthogonal portsof a linear polarity antenna while maintaining their inverse phaserelationship. The linearly polarized first data signal is, for example,a horizontally polarized data signal and the inverse of the linearlypolarized first data signal is, in this example, a vertically polarizeddata signal. The phase and amplitude are adjusted if necessary beforetransmission of the first data signal and the inverse of the first datasignal for enabling the first data signal and the inverse of the firstdata signal to cancel each other out when received together or combined.Complete cancellation of two electromagnetic signals occurs when twoidentical signals that are 180 degrees out of phase and of equalamplitude are combined or received together. The first data signal andthe inverse of the first data signal are transmitted from the samelocation and exactly 180 degrees out of phase such that these signalscan maintain their phase relation as they propagate through space.

Looking down the transmit axis, the nulls of the two inverse signalsoccur at ±45 degrees from the vertical and identically ±45 degrees fromthe horizontal as illustrated in FIG. 3. The nulls refer to regionsaround the transmit axis where there is no measurable power from thefirst data signals to interfere with other signals. A linear dipole atthese rotations will receive zero power from the first data signal S1and the inverse of the first signal S1 ⁻¹.

In an embodiment, the second data signal S2 and the third data signal S3are polarized in orthogonal linear polarities, also referred to ashorizontal and vertical linear polarities, and transmitted. One of thesetwo data signals, for example, the second data signal S2, is transmittedat 45 degrees around the transmit axis from the first data signal S1,and the third data signal S3 is transmitted at 90 degrees off axis from,or orthogonal to, the vertically polarized second data signal S2. Thethird data signal is consequently transmitted −45 degrees off axis fromthe S1 data signal. As a result, the data signals S2 and S3 aretransmitted in the power nulls of S1 and S1 ⁻¹ such that the datasignals S1 and S1 ⁻¹ do not interfere with the data signals S2 and S3 atreception, and thus reception of the data signals S2 and S3 occurs as itnormally would in the absence of S1 and S1 ⁻¹.

FIG. 2 illustrates a system for transmitting electromagnetic signalsover a single frequency using multiple linearly polarized data signals.The system 200 comprises a transmitting station 201 and a receivingstation 202. The transmitting station 201 comprises a data source 201 a,a transmitter 201 b, a polarizer 201 c, and an antenna 201 d. The datasource 201 a provides multiple data signals conveying first data, seconddata and third data over a single frequency. The transmitter 201 bcomprises one or more transmission devices for transmitting each of thedata signals. The polarizers 201 c polarize each of the data signals ina linear polarization scheme. The antennae 201 d at the transmittingstations 201 transmit each of the linearly polarized data signalscomprising the first data signal, the inverse of the first signal, thesecond data signal, and the third data signal to each of one or morereceiving stations 202.

The transmitter 201 b transmits the first data signal and an inverse ofthe first data signal in two orthogonal linear polarities of a linearpolarization scheme. One of the transmitters 201 b transmits the seconddata signal in a linear polarity with a 45 degree rotation around thetransmit axis of either the first data signal or the inverse of thefirst data signal. The second data signal is transmitted from either asame location as the first data signal or a different location from thefirst data signal. The receiving stations 202 receive the transmittedfirst data signal, the inverse of the first data signal, the second datasignal and the third data signal. A receiving station 202 comprises anantenna 202 a of, for example, linear polarity and a receiver 202 b. Thereceiver 202 b receives the transmitted data signals. The antenna 202 aof linear polarity receives the linearly polarized data signals.

In an embodiment, one of the transmitters 201 b also transmits the thirddata signal in linear polarity with a 315 degree or equivalently −45degree rotation around the transmit axis of either the first data signalor the inverse of the first data signal. The second data signal and thethird data signal are orthogonal to each other at the point oftransmission.

FIG. 3 exemplarily illustrates the transmit nulls of the first datasignal S1 and the inverse of the first data signal S1 ⁻¹. These nullsrepresent the regions around the transmit axis where the transmittedpower is zero for the first data signal and the inverse of the firstdata signal.

FIG. 4 exemplarily illustrates the relative rotation around the transmitaxis of the first data signal S1, the inverse of the first signal S1 ⁻¹,the second data signal S2, and the third data signal S3. FIG. 4 alsoshows the polarization around the transmit axis. A receive antenna 202 acan be represented by a dipole. Normally, three signals could not bebroadcast along the same transmission path due to interference issues.However, by transmitting the two orthogonal S1 and S1 ⁻¹ data signals,S2 and S3 data signals see no interference from S1 and S1 ⁻¹ datasignals. Conversely, by using a summation of S1 and S1 ⁻¹ re-invertedsignals, interference from S2 and S3 data signals can be eliminated fromthe first data signal S1.

It is known that the power of an unaligned linear polarized signalreceived in a linear dipole is represented by P=A cos² θ, where θ is theangle between the rotation of the transmitted signal and the rotation ofthe receive dipole, A is the amplitude of the signal received by acorrectly aligned dipole, and P is the relative receive power level atthe specified angle θ. This is known as the polarization loss factor(PLF). The equation representing the resulting amplitude of the sum ofmultiple identical sine waves received at different phase angles isgiven as follows:Y=A sin x+B sin(x+P2)+C sin(x+P3) . . . ,wherein P2 and P3 represent the phase angles of the second and thirdwaves with respect to the first, and A, B and C represent the amplitudesof the corresponding waves.

Combining the two equations, the power level received by a dipole aroundthe transmit axis at any angle θ from either of the transmitted inverseorthogonal linear signals is represented as follows:

$\begin{matrix}{Y = {{\cos^{2} \ominus \;{\sin\; x}} + {{\cos^{2}\left( {90 - \ominus} \right)}{\sin\left( {x + {180{^\circ}}} \right)}}}} \\{= {{\cos^{2} \ominus \;{\sin\; x}} - {{\cos^{2}\left( {90 - \ominus} \right)}\sin\;{x.}}}}\end{matrix}$

Solving for Y, it can be seen that nulls, where the amplitude of theinverse orthogonal data signals S1 received by a dipole are zero, occurat 45°, 135°, 225°, 315° around the transmit axis. Since there are nointerfering S1 signals at these alignments, these alignments are wherethe horizontal and vertical data signals S2 and S3 are transmitted.Also, since these are nulls, receiving the horizontal and vertical datasignals S2 and S3 only requires the alignment of the receive dipole tothe transmit dipole. Having zero power at this rotation, the datasignals S1 and its inverse S1 ⁻¹ do not interfere with the data signalsS2 and S3.

The two inverted first data signals need to be transmitted from the sametransmitting station 201 so as to maintain the inverse phaserelationship as these signals propagate through the medium. The datasignal S2 can be transmitted from any location as long as the rotationalangle of the S2 data signal is plus or minus 45 degrees from that of theS1 and S1 ⁻¹ data signals.

In order to receive the linear second data signal, a receive antenna oflinear polarity is aligned to the transmitting station. For example, thereceived S2 data signal in vertical polarity is aligned with thetransmitted S2 data signal in vertical polarity. Since the nulls offirst data signal and its inverse align exactly with the transmissionrotation of the second data signal, there is no interference from thefirst data signal and its inverse with the antenna receiving the seconddata signal. The data signal S3 is orthogonal to the data signal S2, andhence does not interfere with S2 either. The second linear data signalS2 is received as it normally would be without interference from S1, S1⁻¹ and S3 data signals. Only a single polarity receive antenna alignedto the transmitted S2 data signal is required.

In order to receive the third data signal, a receive antenna of linearpolarity is aligned to the transmitting station. For example, thereceived S3 data signal in horizontal polarity is aligned to the S3transmit horizontal polarity. Since the nulls of first data signal andits inverse align exactly with the transmission rotation of the thirddata signal, there is no interference from the first data signal and itsinverse with the antenna receiving the third signal. The data signal S2is orthogonal to the data signal S3, and hence does not interfere withS3. The third linear data signal S3 is received as it normally would bewithout interference from S1, S1 ⁻¹, and S2 data signals. Only a singlepolarity receive antenna aligned to the transmitted S3 data signal isrequired.

To receive the first data signal, an antenna 202 a with both verticaland horizontal receive polarities is used. The receive antenna 202 amust be aligned to pick up the selected two inverse S1 signals in thetwo receive linear ports, for example, the vertical and horizontalports. One of the set of data signals received in either the horizontalpolarity or the vertical polarity is inverted, and one of the set ofdata signals is phase adjusted if necessary such that the linear S1signals match in phase. The first polarity signal is summed with the nowtwice inverted signal set from the second polarity. When the datasignals are inverted and summed together, the two S1 data signals matcheach other, thereby increasing the signal strength of the first datasignal. Since the two interfering second and third polarized datasignals are received at equal levels in both linear ports, and one ofthe two received signals is inverted and then summed with the other, theinterfering second data signals negate at summation resulting in minimalinterference. This can be represented by the following equations:Received in the horizontal port: S1+S2 cos² 45°±S3 cos² 45°Received in the vertical port: S1⁻¹ +S2 cos² 45°±S3 cos² 45°

Invert one and sum (combine) with the other as follows:Srx=S1+S2 cos² 45°±S3 cos² 45°±S1−S2 cos² 45°−S3 cos² 45°=2S1.

In other words, the interfering S2 and S3 data signals cancel uponinversion and summation, and the received signal Srx is S1 with twicethe power.

In another embodiment, either the second data signal S2 or the thirddata signal S3 can be deleted and no signal sent in that polarity. Forexample, only the vertical polarity data signal S2 can be transmittedalong with S1 and S1 ⁻¹ data signals.

In an alternative embodiment, both the vertical S2 data signal and thehorizontal S3 data signal are the same signal transmitted in phase, butorthogonal to each other. In this embodiment where the S2 and S3 signalsare the same and in phase, the receive antenna polarizations do not needto be aligned to the transmit antenna polarizations. Antennae 102 a thatcan receive both horizontal and vertical polarities are required. Thereceive antenna 102 a can be represented by two orthogonal dipoles. Whensummed together, it can be seen that the rotation of the receive dipolesaround the transmit axis does not matter when receiving the S2 datasignal allowing for use in mobile applications.

In another embodiment, in order to receive the S2 data signal withoutinterference, both orthogonal receive elements, for example, horizontaland vertical receive elements receiving signals in equal strength areused. Alternatively, the strength of the two poles is electronicallyadjusted such that the amplitudes of the two polarities are equal. Inorder to detect the second data signal S2, the received signal in thehorizontal linear receive polarity is summed with the received signal inthe orthogonal polarity.

The following equations describe the power levels of the receivedinterfering signals S1 and S1 ⁻¹. In the horizontal (H) and vertical (V)polarities, where θ is the angle between the interfering S1 signal andone receive linear dipole, and 90-θ is the angle between the othertransmitted signal S1 ⁻¹ and the same selected linear receive dipole,Hrx is the signal received in the horizontal dipole and Vrx is thesignal received in the orthogonal dipole:Hrx=S1 cos² θ sin x+S1 cos²(90−θ)sin(x+180°)Vrx=S1 cos²(θ)sin(x+180°)+S1 cos²(90−θ)sin(x)

Combining the above two equations together:

$\begin{matrix}{{Srx} = {{Hrx} + {Vrx}}} \\{= {{{S\; 1\cos^{2}} \ominus \;{\sin\; x}} - {S\; 1{\cos^{2}\left( {90 - \ominus} \right)}{\sin(x)}} - {S\; 1{\cos^{2}( \ominus )}{\sin(x)}} +}} \\{S\; 1{\cos^{2}\left( {90 - \ominus} \right)}\sin\;(x)} \\{= 0.}\end{matrix}$

Hence the interfering inverse S1 data signals cancel upon summation ofthe received signals in the receiving station 202, irrespective of therotation of the receive dipoles in relation to the transmit dipoles. Thepower equations for the second data signal S2, received in the twopolarities H and V are as follows:Hrx=S2 cos²(θ)+S2 cos²(90−θ)Vrx=S2 cos²(90−θ)+S2 cos²(θ)

Combining the signals received in the two ports, viz. horizontal andvertical ports:H+V=2 S2 cos²(θ)+2 S2 cos²(90−θ)=2 S2(cos²(θ)+sin²θ)=2 S2.

Hence, the power level of the desired data signal S2 always sums to twotimes S2 irrespective of the rotation of the two receive dipoles aroundthe transmit axis in relation to the two transmit dipoles, while theunwanted data signals S1 and S1 ⁻¹ always sum to zero power.

In summary, upon summing the two receive polarities, Hrx and Vrx of thereceive antenna 202 a, the interfering inverse data signals S1 and S1 ⁻¹always sum to zero, and the desired second data signal S2 transmitted inhorizontal and vertical polarities always sum to two times S2 (fullpower). The rotation around the transmit axis does not matter. If thereis another rotation along the Z axis, for example, away or toward thetransmitter, it is possible to adjust the received levels such that theamplitude of each dipole is equal and hence the interfering receivedsignals cancel.

In order to detect the first data signal S1, instead of summing thesignals received in the two polarities, one of the two signals is phasechanged 180 degrees (inverted) and then summed with the other. Lookingat the interfering linear data signals S2 in vertical and horizontalpolarizations, it can be seen that inverting one of the two polarizedreceived signals and summing with the other of the two polarizedreceived signals from the two receive polarities cancels out theinterfering data signals S2, irrespective of the rotation around thetransmit axis of the receive dipoles, leaving S1 alone withoutinterference from S2.

The signals received by Hrx and Vrx poles (unaligned) are represented asfollows, where θ and 90-θ are the rotational angles between the transmitdipoles of data signal S2 in H and V polarities, respectively, and thereceive dipoles:Hrx=cos² θ sin x+cos²(90−θ)sin(x)Vrx=cos²(90−θ)sin(x)+cos² θ sin x.

Inverting one by changing the phase by 180 degrees, the sum of the twosignals becomes:

$\begin{matrix}{P = {{\cos^{2} \ominus \;{\sin\; x}} + {{\cos^{2}\left( {90 - \ominus} \right)}\sin\;(x)} + {{\cos^{2}\left( {90 - \ominus} \right)}\;{\sin\left( {x + 180} \right)}} +}} \\{\cos^{2} \ominus \;{\sin\left( {x + 180} \right)}} \\{{= {{\cos^{2} \ominus \;{\sin\; x}} + {{\cos^{2}\left( {90 - \ominus} \right)}{\sin(x)}} - {{\cos^{2}\left( {90 - \ominus} \right)}{\sin(x)}} - {\cos^{2} \ominus {\sin(x)}}}}\;} \\{= 0.}\end{matrix}$

Hence the interfering data signals S2 in H and V polarities cancel uponinversion of one and summation to the other.

Options are available to detect the desired data signal S1, where T isthe angle between one of the transmit polarities and the receive dipole,and 90°−T is the rotational angle between the other transmit polarityand the same receive dipole. The following equations represent thesignals received:Hrx=cos² T sin x+cos²(90°−T)sin(x+180°)Vrx=cos² T sin(x+180°)+cos²(90°−T)sin x

Inverting one of the above equations and summing:

$\begin{matrix}{P = {{H\;{rx}} + {Vrx}}} \\{= {{\cos^{2}T\;\sin\; x} + {{\cos^{2}\left( {{90{^\circ}} - T} \right)}{\sin\left( {x + {180{^\circ}}} \right)}} + {\cos^{2}T\;{\sin\left( {x + {180{^\circ}} - {180{^\circ}}} \right)}} +}} \\{{\cos^{2}\left( {{90{^\circ}} - T} \right)}{\sin\left( {x - {180{^\circ}}} \right)}} \\{= {{\cos^{2}T\;\sin\; x} - {{\cos^{2}\left( {{90{^\circ}} - T} \right)}{\sin(x)}} + {\cos^{2}T\;{\sin(x)}} - {{\cos^{2}\left( {{90{^\circ}} - T} \right)}{\sin(\; x)}}}} \\{= {2{\left( {{\cos^{2}T\;\sin\; x} - {{\sin^{2}(T)}\;{\sin(x)}}} \right).}}}\end{matrix}$

It can be seen that a rotation around the transmit axis causes a dropoff in signal strength of S1 to zero as the orthogonal receive dipolesapproaches a 45 degree rotation from the transmit dipoles, and then thesignal strength starts to gain again.

In summary, by receiving both horizontal and vertical polarity signals,and inverting one and summing with the other, the interfering S2 signalcancels out. However, the rotation of the receive antenna 202 a aroundthe transmit axis influences the signal strength of the first datasignal S1 at a receive dipole. Various approaches can be used to alwaysreceive a detectable S1 signal. One choice is to provide few degrees ofalignment of the receive poles with the transmit poles such that therotational angle of the receive polarities is close to the angle of thetransmit polarities. For example, if the receive antenna 202 a can bemaintained within a fifteen degree rotation of the transmit antennapoles, then the receive antenna 202 a would receive power at about atleast 75% of a fully aligned antenna. Alternatively, the alignmentproblem can be addressed by having two sets of orthogonal receiveantennae 202 a each at a 45 degree rotation from the other. Theelectronic controller 202 c can select the antenna 202 a with the highergain, thus allowing a complete 360 degree rotation of the receiveantenna 202 a around the transmit axis.

FIG. 5 exemplarily illustrates a flow chart for reception of datasignals at a receiving station 202 for acquiring the first data signal.The first data signal and the inverse of the first data signal arereceived 501 at the receiving stations 202 in the linear polarizationscheme. One of the first data signal and the inverse of the first datasignal is inverted 502 and summed 503 with the other of the first datasignal and the inverse of the first data signal to yield the first datasignal at an increased strength. The received second data signal cancelsout at summation. In the case where the second and third data signalsare not identical, both the received second data signal and the receivedthird data signal cancel out at summation.

FIG. 6 exemplarily illustrates a flow chart for reception of datasignals at a receiving station 202 for acquiring the second data signalwhen S2 and S3 are the same and in phase. In this example, the rotationof a receive antenna feed in relationship to a transmit antenna feed isunaligned. The second data signal is received 601 at the receivingstations 202 in both the orthogonal linear polarities. The receivedsecond data signal in one of the orthogonal linear polarities iscombined 602, in phase, with the received second data signal in theother of the orthogonal linear polarities to reduce interference fromthe first data signal and the inverse of the first data signal.

In another embodiment, a first set of two orthogonal poles receives thefirst data signal, the inverse of the first data signal, and the seconddata signal. A second set of orthogonal poles also receives the firstdata signal, the inverse of the first data signal, and the second datasignal. An electronic controller 202 c at one or more receiving stationsselects either the first set of two orthogonal poles or the second setof two orthogonal poles for retrieving the first data signal at maximumreception strength of the first data signal. In a three dimensionalversion, multiple sets of orthogonal dipoles can be located alongvarious axis. The electronic controller 202 c can then select from thebest pair of orthogonal dipoles at any particular instant.

In another embodiment of the receive antenna, the antenna 202 a isdesigned or configured to emulate or function as a gyroscope. In thisconfiguration, the vertical polarity dipole is used as the center axisof the gyroscope. The horizontal antenna is a disk that rotates aroundthe vertical axis. The rotation of the disk keeps the antenna 202 a gyrostabilized such that the axis is always parallel to the vertical axis ofthe transmit antenna, and preferably perpendicular to the Earth'ssurface. The horizontal antenna picks up the horizontally polarizedsignal preferably parallel to the Earth's surface.

FIG. 7 exemplarily illustrates a configuration for a gyroscopic receiveantenna. The spindle of the antenna is a rotating shaft 701 that alsoacts as the vertical receive dipole. The entire assembly 700 is gimbaled703 to allow the momentum of the device to gyro stabilize itself. Thegimbal 703 is manufactured of material transparent to the selectedelectromagnetic signals. The platform 702 rotates around and with theshaft 701. This platform 702 forms the horizontal receive dipole. Thereceive electronics 705 can be mounted on the platform 702. The motor704 turns the shaft 701 and the platform 702 at a high velocity. Also,the motor 704 adds weight to the lower end of the spindle such that whenthe spindle winds down, the vertical shaft 701 aligns perpendicular tothe Earth as a result of gravity. The resulting received signal can berelayed by electromagnetic signals to additional electronics at thereceiving station 202.

FIGS. 8A and 8B exemplarily illustrate a typical implementation of themethod to transmit and receive three distinct data signals on the samefrequency simultaneously. The first data signal is encoded and amplifiedby transmitter A 801A, and split into two signals by a splitter 802. Onecopy is phase adjusted by 180 degrees forward or backward by a phaseinverter 803. The S1 signal is transmitted in the horizontalpolarization through the antenna 804A. The S1 ⁻¹ signal is transmittedin the vertical polarization through the antenna 804B.

S2 is transmitted at a 45 degree rotation from S1 by transmitter B 801Bthrough antenna 804C. S3 is transmitted at a 90 degree rotation, thatis, orthogonally from S2 by transmitter C 801C through antenna 804D.

S1 horizontal is received in the horizontal polarity of antenna 820A. S1⁻¹ is received in the vertical polarity of antenna 820A. S1 ⁻¹ isinverted back to being in phase with S1 by a 180 phase shifter 823. Thetwo received signals are combined in phase at the combiner 824.Additional decoding and detection is performed by receiver C 821Aresulting in the output of the first data signal S1.

S2 is received in the horizontal polarity of antenna 820C which isaligned to the transmit polarity of the antenna 804C. The received S2signal is processed in receiver A 821C resulting in the output of thesecond data signal S2. S3 is received in the vertical polarity ofantenna 820D which is aligned to the transmit polarity of the antenna804D. The received S3 signal is detected and decoded in receiver B 821Dresulting in the output of the third data signal S3.

The foregoing examples have been provided merely for the purpose ofexplanation and are in no way to be construed as limiting of the presentinvention disclosed herein. While the invention has been described withreference to various embodiments, it is understood that the words, whichhave been used herein, are words of description and illustration, ratherthan words of limitation. Further, although the invention has beendescribed herein with reference to particular means, materials, andembodiments, the invention is not intended to be limited to theparticulars disclosed herein; rather, the invention extends to allfunctionally equivalent structures, methods and uses, such as are withinthe scope of the appended claims. Those skilled in the art, having thebenefit of the teachings of this specification, may affect numerousmodifications thereto and changes may be made without departing from thescope and spirit of the invention in its aspects.

I claim:
 1. A method for transmitting electromagnetic signals,comprising: providing said electromagnetic signals conveying first dataand second data, wherein said electromagnetic signals are of a samefrequency, and wherein said electromagnetic signals comprise a firstdata signal conveying said first data and a second data signal conveyingsaid second data; transmitting said first data signal and an inverse ofsaid first data signal respectively in two orthogonal linear polaritiesof a linear polarization scheme so as to maintain their inverted phaserelationship once propagated; and transmitting in a linear polarity saidsecond data signal in a power null of said transmitted first data signaland said transmitted inverse of said first data signal.
 2. The method ofclaim 1, wherein transmitting said second data signal further comprises:transmitting said second data signal in a linear polarity with a 45degree rotation around a transmit axis of one of said transmitted firstdata signal and said transmitted inverse of said first data signal,wherein said second data signal is transmitted from one of a samelocation as said first data signal and a different location from saidfirst data signal.
 3. The method of claim 1, further comprising:providing a data signal conveying third data, wherein said data signalis of same frequency as said first and second data signals, and whereinsaid data signal comprises said third data signal conveying third data;and transmitting said third data signal in a linear polarity, whereinsaid third data signal is transmitted orthogonally to said second datasignal.
 4. The method of claim 1, further comprising: receiving saidtransmitted second data signal at one or more receiving stations, in anantenna aligned with transmitted polarity of said second data signal. 5.The method of claim 1, further comprising: receiving said first datasignal and said inverse of said first data signal at said one or morereceiving stations in said orthogonal linear polarities; inverting oneof said received first data signal and said received inverse of saidfirst data signal; and summing in phase said inverted one of saidreceived first data signal and said received inverse of said first datasignal with the other of said received first data signal and saidreceived inverse of said first data signal to yield said first datasignal at increased strength, wherein received interfering second datasignals cancel at summation.
 6. The method of claim 3, wherein saidthird data signal is identical to said second data signal and propagatedin phase with said second data signal.
 7. The method of claim 6, furthercomprising: receiving said second data signal and said third data signalby a receive antenna capable of receiving both horizontal and verticallinear polarities, wherein said receive antenna is aligned or unalignedto said polarities of said transmit antenna; and combining in phase ofsaid second data signal, said received signals from said horizontal andvertical linear polarities to yield said second data signal at increasedstrength, wherein received first data signals cancel at summation. 8.The method of claim 6, further comprising: receiving said transmittedfirst data signal, said transmitted inverse of said first data signal,and said transmitted second data signals utilizing a first set of twoorthogonal poles; receiving said transmitted first data signal, saidtransmitted inverse of said first data signal, and said transmittedsecond data signals utilizing a second set of orthogonal poles; and forsaid received signals of each set of said orthogonal poles, invertingone of said received first data signal and said received inverse of saidfirst data signal, and summing said inverted one of said received firstdata signal and said received inverse of said first data signal with theother of said received first data signal and said received inverse ofsaid first data signal to yield said first data signal at increasedstrength, wherein received interfering second data signals cancel atsummation.
 9. The method of claim 8, further including for each ofoutput signal from said summations performing one of: a) selecting oneof said first set of two orthogonal poles and said second set of twoorthogonal poles for retrieving said first data signal at maximumreception strength of said received first data signal; or b) summing thesummed output results from said first set of orthogonal poles in phasewith the summed output results from said second set of orthogonal polesto retrieve said first data signal at increased strength.
 10. The methodof claim 9, further comprising: including additional dual polarityreceive antennas to receive said transmitted first data signal, saidtransmitted inverse of said first data signal, and said transmittedsecond data signals utilizing said orthogonal poles rotated around thetransmit axis from said first set of orthogonal poles and from saidsecond set of orthogonal poles; for the received signals of each set oforthogonal poles, inverting one of said received first data signal andsaid received inverse of said first data signal; summing said invertedone of said received first data signal and said received inverse of saidfirst data signal with the other of said received first data signal andsaid received inverse of said first data signal to yield said first datasignal at increased strength, wherein received interfering second datasignals cancel at summation; for each of said output signals from saidsummations performing one of the following: a) selecting one of saidsummations for retrieving said first data signal at maximum strength; orb) summing the summed output results from said first set of orthogonalpoles in phase with summed output results from each additional set oforthogonal poles to retrieve said first data signal at increasedstrength.
 11. The method of claim 6, further comprising providing a spinstabilized receive gyroscopic antenna with a vertical dipole built intothe rotating shaft and a horizontal dipole built into the rotatingplatform at said one or more receiving stations to pick up saidtransmitted orthogonal linear signals.
 12. A method for communicatingelectromagnetic signals, comprising: providing said electromagneticsignals conveying first data, second data and third data, wherein saidelectromagnetic signals are of a same frequency, and wherein saidelectromagnetic signals comprise a first data signal conveying saidfirst data, a second data signal conveying said second data, and a thirddata signal conveying said third data; transmitting said first datasignal and an inverse of said first data signal in two orthogonal linearpolarities of a linear polarization scheme, said first data signal andsaid inverse of said first data signal maintaining their 180 degreephase relationship as propagated; transmitting said second data signaland said third data signal in the power nulls of said first data signaland said inverse of said first data signal, wherein said second datasignal and said third data signal are transmitted orthogonally to eachother.
 13. The method of claim 12, wherein transmitting said second datasignal and said third data signal further comprises: transmitting saidsecond data signal in a linear polarity with a 45 degree rotation arounda transmit axis of one of said transmitted first data signal and saidtransmitted inverse of said first data signal, wherein said second datasignal is transmitted from one of a same location as said first datasignal and a different location from said first data signal; andtransmitting said third data signal in said linear polarity with a 315degree rotation around the transmit axis of one of said transmittedfirst data signal and said transmitted inverse of said first datasignal, wherein said third data signal is transmitted orthogonally tosaid second data signal; and wherein said third data signal istransmitted from one of said same location as said first data signal andsaid different location from said first data signal.
 14. The method ofclaim 12, further comprising receiving said transmitted signals at oneor more receiving stations, wherein said receiving said transmittedsignals further comprises: receiving said transmitted first data signaland said inverse of said first data signal in orthogonal linearpolarizations; inverting one of said received first data signal and saidreceived inverse of said first data signal; and summing said invertedone of said received first data signal and said received inverse of saidfirst data signal with the other of said received first data signal andsaid received inverse of said first data signal to yield said first datasignal at increased strength, wherein interfering said received seconddata signals cancel at summation, and wherein interfering said thirddata signals cancel at summation.
 15. The method of claim 14, furthercomprising: at said one or more receiving stations, receiving saidsecond data signal at a linear polarity antenna aligned to polarity ofan antenna transmitting said second data signal, thereby receiving saidsecond data signal with low interference; and at said one or morereceiving stations, receiving said third data signal at a linearpolarity antenna aligned to polarity of an antenna transmitting saidthird data signal, thereby receiving said third data signal with lowinterference.
 16. A system for transmitting electromagnetic signals,comprising: a data source for providing a plurality of data signalsconveying first data, second data and third data, wherein said datasignals are of a same frequency, and wherein said data signals comprisea first data signal conveying said first data, a second data signalconveying said second data, and a third data signal conveying said thirddata; one or more transmitting devices for transmitting said first datasignal and an inverse of said first data signal in two orthogonal linearpolarities respectively of a linear polarization scheme; said one ormore transmitting devices for transmitting said second data signal in alinear polarity with a 45 degree rotation around a transmit axis of oneof said transmitted first data signal and said transmitted inverse ofsaid first data signal, wherein said second data signal is transmittedfrom one of a same location as said first data signal and a differentlocation from said first data signal; and said one or more transmittingdevices for transmitting said third data signal in a linear polarity,said third data signal transmitted orthogonally to said second datasignal, wherein said third data signal is transmitted from one of saidsame location as said first data signal and said different location fromsaid first data signal, and one of said same location as said seconddata signal and said different location from said second data signal.17. The system of claim 16, further comprising one or more receivingstations including at least one of: a first single polarity receiveantenna aligned to said polarity of said transmitting device of saidsecond data signal for receiving said second data signal with lowinterference from said first data signal and said inverse of said firstdata signal which cancel each other at reception; or a second singlepolarity receive antenna aligned to said polarity of said transmittingdevice of said third data signal for receiving said third data signalwith low interference from said first data signal and said inverse offirst data signal which cancel each other at reception; or a dualpolarity receive antenna aligned to said polarities of said transmittingdevice of said second and third data signals for receiving said secondand third data signals with low interference from said first data signaland said inverse of first data signal which cancel each other atreception; or a dual polarity receive antenna aligned to said polaritiesof said transmitting device of said first data signal and its inverse,inverting one of said received first data signal and said receivedinverse of said first data signal, and summing said inverted one of saidreceived first data signal and said received inverse of said first datasignal with the other of said received first data signal and saidreceived inverse of said first data signal to yield said first datasignal at increased strength, wherein interfering said received seconddata signals cancel at summation, and wherein interfering said thirddata signals cancel at summation.
 18. A method for communicatingelectromagnetic signals, comprising: providing a plurality ofelectromagnetic signals conveying first data, second data and thirddata, wherein said electromagnetic signals are of a same frequency, andwherein said electromagnetic signals comprise a first data signalconveying said first data, a second data signal conveying said seconddata, and a third data signal conveying said third data, wherein saidsecond and third data signals occupy orthogonal linear polarities;generating an inverse copy of said first data signal; transmitting, in alinear polarization scheme, said first data signal at a 45 degreerotation around a transmit axis from said second data signal; andtransmitting said inverse of said first data signal at a 135 degreerotation around the transmit axis from said second data signal; saidfirst data signal and said inverse of said first data signal propagatedso as to maintain their 180 degree or inverted phase relationship oncetransmitted; and thereby increasing capacity in a electromagnetictransmission system.
 19. The method of claim 18, further comprising:receiving said first data signal and said inverse of said first datasignal, wherein receiving said first data signal and said inverse ofsaid first data signal further comprises: inverting one of said receivedfirst data signal and said received inverse of said first data signal;and summing said inverted one of said received first data signal andsaid received inverse of said first data signal with the other of saidreceived first data signal and said received inverse of said first datasignal to yield said first data signal at increased strength, whereinsaid interfering received third data signal and second data signalcancel at summation.
 20. A method for receiving electromagnetic signals,comprising: receiving a transmitted data signal and an inverse of saidtransmitted data signal in orthogonal polarities; inverting one of saidreceived data signal and said received inverse of said data signal; andcombining in phase said inverted one of said received data signal andsaid received inverse of said data signal with other of said receiveddata signal and said received inverse of said data signal to yield saidreceived data signal at increased strength, wherein received interferingdata signals cancel at summation.